A stacker includes a medium stacking portion for receiving and stacking a medium processed and discharged by a processing unit, a medium butting portion for aligning the medium by contacting a leading end of the medium, and a paddle that includes a feeding portion and is for transporting the medium received by the medium stacking portion in a direction toward the medium butting portion by rotating. Furthermore, the stacker has a first mode in which the paddle stops in a state in which the feeding portion does not contact the medium on the medium stacking portion and a second mode in which the paddle stops in a state in which the feeding portion comes into contact with the medium on the medium stacking portion and is deformed.